Desensitization to azathioprine

Azathioprine is an immunosuppressant drug which is an analog to 6-mercaptopurine and has been used in the last 20 years to prevent organ transplant rejection. It has also been used in the treatment of some autoimmunological diseases. We present a case of a 24-year-old woman with systemic lupus erythematosus, suffering from nephritis, who developed angioedema after using azathioprine to control her illness. She had never reported similar episodes. The involvement of the drug was demonstrated by positive oral challenge test without changes in biochemical and complement blood determinations. She reached tolerance to the drug after a desensitization procedure (increasing 5 mg each day to reach 125 mg daily). We are not able to propose the involvement of an IgE-mediated mechanism, but rather a hypersensitive one with a non-dose-dependent effect. These desensitization procedures show great potential as therapeutic safeguards against harmful drugs in some patients. We have not found any other desensitization procedure for this drug.